As a long time volvo technician I've been seeing alot of s40, v50, c30, c70 left side upper radiator hoses fail. The car dose not have a coolant level sensor, And this engine overheats extremely fast. If your car has over a 100k miles on it I'd replace it. Its a moderately expensive repair but it beats needing an engine. Today I had a customer, Just bought a used v50 t5 awd, Very nice car, Just put 4 tires, And new rims on it. Poor guy broke the hose now he needs a 5,000 dollar engine replacement. Its becoming to common.